This invention relates generally to a method of using evenly distributed air flow to condition glass filaments prior to the application of a sizing material on the glass filaments.
The use of a flow of air across glass filaments has been used to improve the environment of the fiber forming process. In particular, U.S. Pat. No. 4,088,469 discloses a fiber forming system employing horizontally directed air in combination with a horizontally oriented air jet to entrain additional air to control the environment of the fiber-forming bushing. In particular, the invention requires a generally horizontal high velocity stream of gas which controls the environment of the bushing.
U.S. Pat. No. 4,033,742 discloses a cooling system of a bushing used in the production of glass fibers which embodies a heated orifice plate with closely placed orifices in a bulk flow of upwardly directed gas. The cooling system comprises a series of opposing nozzles which provide a multiple air lance effect and starting-up, clearing and maintaining the flow of individual glass fibers through each orifice.
U.S. Pat. No. 3,969,099 discloses a bushing environmental system wherein an air stream is passed directly to the region below the bushing from a blower which diverts and irregularly deflects the air stream prior to its release through the bushing region. The air is fed to the fiber glass bushing at about a right angle to the bushing tips.
U.S. Pat. No. 4,197,103 discloses a method for draw forming glass fibers wherein cooling fins extend outwardly from a water pipe and disposed between rows of conical nozzle tips. Additional cooling is provided at least during the initial start-up period by air blown across the nozzle tips. After stabilized filament forming conditions have been reached, usually within 5-10 seconds, the air flow is reduced or terminated.
However, these above-described methods do not reduce migration of sizing material from glass fibers. Most continuous glass fibers have an extended drying period, which sometimes lasts for several days. As water evaporates from the glass surface and as more water migrates to the surface, the water carries components of the size with it. This results in a concentration of dried fiber size on the surface of the fiber which at times can be three times what it is in the middle. Such variations cause undesirable handling changes. Also, when the glass fibers are wound on a collet often the outer layers of the package must be discarded thus causing significant loss in glass fiber.
There has now been invented an improvement of the use of airflow to condition glass filaments prior to the application of a sizing material on the glass filaments. This invention is directed to that improvement.